How to create exact (CAD-like) hard-surface shapes

[GeeJay]

Hi!

i am currently investigating how to use 3D-Coat for precise hard surface modeling and I find it much more challenging than sculpting because it is so unforgiving. So I'd like to ask from time to time how to model a specific shape I am having problems with. If this is the wrong place for this topic please move it!

The first shape is this:

The end has to be an exact circle. The problem I am having is with creating this circular shape and also with deforming the whole object, I tried the free-form primitives and the free-form pose mode, but the deform cage either has not enough control or it is too dense. I can't get a good selection.

I am certain the tools are there to do it, I just don't see them, so I'd like to get some tips to get into the 3D-Coat way of thinking.

And one more questions: Are there methods for doing precise selections, can I type in a radius or snap to the grid with the selections?

Thanks!

[TimmyZDesign]

There are several ways to do this.

You can use the Sketch Tool:

Or:

First create two cylinders (on separate Voxel layers) with the Primitives tool:

Then use BasRelief Tool to create the necessary voxels inbetween the cylinders:

Merge the two volumes. Then Use Cutoff Tool ("draw with closed spline" mode) to cut off unneccesary voxels:

Duplicate and "ghost" the original volume, then Transform it downwards with the Transform Tool:

Subtract the duplicated volume from the original volume (right-click on the voxel layer and choose "Subtract From"):

Smooth as needed (using Smooth All in Voxel menu). You are done!

[GeeJay]

Wow, thank you so much for taking the time for this post. The bas-relief tool! See, that's what I meant: I would never have gotten the idea it could be used for this, but now that I have an idea that it can be applied this way a whole lot of possibilities open up.

[polyxo]

Without trying to bash TimmyZDesign's approach:

Creating such shapes would work quite different in CAD-programs and it would take less steps.

Draw precises outer contour line by using numerical input, extrude, trim with a line, surface or body.

Indeed with Voxels one as a Developer is free in the choice of Geometry creation methods. One could lean towards

the way one would work with in Nurbs or one can instead use principles used in mesh modellers.

Once in a while a user discovers Freeform (Sensable now owned by Geomagic) which is a Voxel based program which

has a lot of CAD geometry creation principles built in. But here Andrew gets most of his feedback/wishes by people who

otherwisely only do mesh modelling and that gets visible in the strategies the program offers.

If you are a CAD modeller I would suggest to simply import your shapes from your preferred software.

[GeeJay]

Thanks for the reply. I am not really a CAD modeler I just have to create a lot of hard surface models. I could have been clearer in that regard, the measurements don't have to be 100% precise but on the other hand most operations using a brush are out too because they are too imprecise. I was looking for something that is faster and allows shapes to be combined, holes to be punched more easily than in a poly/NURBS application but still retains an acceptable amount of sharpness and correctness. I'll still have to see if 3D-Coat makes this possible, for example I'll still have to retopo in the end. It's more of an experiment right now.

If someone uses 3D-Coat for this I would be very grateful for tips and pointers.

[TimmyZDesign]

Hard surface modeling in 3D-Coat can be very easy and fast. It is also possible to create very complex hard surface objects in 3D-Coat.

Sometimes it is the very best and fastest way to get the job done.

On the other hand, you should be aware of some things:

1. If you model a very complex object in 3D-Coat, and you do not plan ahead, it is possible that you will not be able to retopologize it easily. Plan ahead. Try to put all the parts on separate layers. Then you can retopo each part on its own, and it will be easier. Also think about reusing parts if possible (so you only need to retopo those once).

2. Sometimes 3D-Coat should only be used as a concept tool. Create your hard surface idea quickly in 3D-Coat, but then rebuild the whole thing slowly in a traditional polygon modeling app like Maya/Max/etc. Having your 3D-Coat model only as a reference can still be extremely useful.

3. Decide if you really need a low poly version of your hard surface object. Remember that you can decimate your high poly object in 3D-Coat to get acceptable poly counts (and still maintain hard edges), and you can vertex paint it too (without needing any UVs). A high poly painted object might be enough for your needs.

[GeeJay]

Concering the decimation / still retaining hard edges, what are your settings for this? Do you use resample?

[TimmyZDesign]

1) While in Surface mode, look at the top of the viewport and you will see an option called "SHIFT action", and there is a dropdown menu next to it. In that dropdown select Decimate.

2) Press the "w" key on your keyboard to toggle wireframe view mode.

3) Then select the LiveClay tool (or almost any brush-type tool), and while holding down the SHIFT key (still in Decimate mode) start to brush on the surface of your high poly object.

4) You will see that the poly count is reduced where you are brushing, but the surface remains visually the same. Of course, when you brush on a hard edge, it will somewhat flatten that edge (because the poly count there will be reduced). If you want to keep that edge hard, then DON'T brush on it. Instead, brush on all of the other flat areas that are not hard edges and those areas will still look the same, but the polycount in those areas will be reduced. Of course this is a little time-consuming, but just spending 15 minutes doing this will very significantly reduce the overall polycount of your model. Your model will then have high polycounts on hard edges, and lower polycounts on flat surfaces. Usually the polycount is still high enough however to get decent vertex-painting results.

5) You can always add more resolution (without affecting the surface) by using a brush-type Live Clay tool and turning down the Depth setting of that brush to "0". Then brushing on the surface will add polygons, but the surface will remain visually the same. (It may be necessary to do this in order to get better vertex-painting resolution on specific parts of your model.)

Edited May 8, 2013 by TimmyZDesign